If your Ford F-150 is running roughly, starting hard or misfiring, you may have a bad oxygen sensor. These are all common symptoms of a faulty O2 sensor. You might, however, also have your "check engine" or "service engine soon" light coming on. The oxygen or O2 sensors are an important part of the engine-management system in your car. They read the amount of oxygen in the exhaust and send the information back to the vehicle's computer. The computer will then make critical adjustments to the system, based on these readings. You can buy a replacement O2 sensor from the dealer or an aftermarket one from most auto parts stores.
Raise the front end of your truck with a jack. Position a set of jack stands under the frame to support it. Locate the oxygen sensors in the exhaust system. You will find one in the pipe just behind the catalytic converter; two others will be further back where the pipe splits before the mufflers.
Disconnect the wiring harness from the front-most sensor by pulling the locking tab on the connector toward you and then sliding the two sections of the connector apart. Do not pull on the wires or you may damage the wiring harness.
Remove the oxygen sensor from the pipe by turning it counterclockwise with a ratchet and oxygen sensor socket. Pull the sensor from the exhaust pipe.
Install the new oxygen sensor into the exhaust pipe. Turn it clockwise with a ratchet and oxygen sensor socket until snug. Tighten the sensor to 36 foot-pounds with a torque wrench.
Install the wiring harness connector. Push the locking tab into the connector to secure it. Move to the downstream sensors and repeat the process to change both of these oxygen sensors as well.
